Spinal cord stimulator implant infection rates decreasing

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A multicentre retrospective study has found that infection rates associated with spinal cord stimulator implants are lower than previously reported and that these rates are now on par with other surgical specialties.

Published in the journal Neuromodulation, the study “Spinal cord stimulator implant infection rates and risk factors: a multicentre retrospective study” looked to establish a modern infection rate for spinal cord stimulators, assess the impact of known risk factors for surgical site infections and to determine the impact of certain preventative measures on the rate of infection.

Bryan Hoelzer, (Mayo Clinic, Rochester, USA) and colleagues write that while spinal cord stimulation is an evidence-based treatment for a number of chronic pain conditions and this therapy offers improvement in pain and function, it is not without potential complications. These complications include device failure, migration, loss of therapeutic paraesthesia, and infection.

To conduct this investigation into infection rates, Hoelzer et al carried out a retrospective review on 2,737 unique implants or revisions of spinal cord stimulation systems. Patient demographics, risk factors including diabetes, tobacco use, obesity, revision surgery, trial length, implant location, implant type, surgeon background, prophylactic antibiotic use, utilisation of an occlusive dressing, and post-operative antibiotic use were recorded and analysed.

The authors found that the overall infection rate in the study cohort was 2.45% (n=67).

“Diabetes, tobacco use, and obesity did not independently increase the rate of infection. Revision surgeries had a trend toward higher infection rate; however, this did not meet statistical significance. There was no difference in the rate of infection between implants performed by physicians of different base specialties, cylinder leads vs. paddle leads, or between different prophylactic antibiotics. Implants performed at academic centres had a higher rate of infection when compared to implants performed in non-academic settings,” the authors report.

Additionally, the study showed that when patients received an occlusive dressing or post-operative antibiotics they had a lower rate of infection.

Hoelzer and colleagues explained that the infection rate (2.45%) reported in this study is lower than the previously reported rates (3–6%) and are on par with other surgical specialties. This study did not show an increased rate of infection for patients that used tobacco, had diabetes or were obese.

“It is possible that given the low overall infection rate a larger study is needed to establish the true impact of these factors on infection. In addition, this study did not address the impact of poorly controlled diabetes mellitus (elevated hemoglobin A1c) versus well-controlled diabetes. It can be concluded from this study that utilising an occlusive dressing over the incision in the post-operative period decreases the rate of infection and should become the standard of care. This study also demonstrated the positive impact of post-operative antibiotics in decreasing the rate of infection. Studies in other surgical specialties have not shown this impact which would suggest that further research is needed,” they conclude.

As to how these results compare to other studies into spinal cord stimulation implant infection rates, the findings are similar. A recent single site review over a 7.5-year follow-up period (Thomson SJ, Kruglov D, Duarte RV 2017. A Spinal Cord Stimulation Service Review From a Single Centre Using a Single Manufacturer Over a 7.5 Year Follow-Up Period. Neuromodulation 2017; E-pub ahead of print. DOI:10.1111/ner.12587) saw a rate of implant infection and device explantation of 2.3%.

Compared to a similar US-based study by Salim Hayek et al (Hayek SM, Veizi E, Hanes M. Treatment-limiting complications of percutaneous spinal cord stimulator implants: a review of eight years of experience from an academic center database. Neuromodulation 2015;18:603–608. Discussion 608–609), this UK-based study had lower infection rates and higher trial to implant rates: “Spinal cord stimulation is delivered there as a separate trial and later a full implantation, rather than staged with temporary extensions. Many experts assume that the staged procedure is associated with a higher incidence of trial and implant infections. Hayek’s team reports a 4.3% implant infection rate. Trial to implant ratio, if high, may indicate comprehensive selection and patient expectation management providing that the explant rate is not too high. On the other hand it may be that some patients who may benefit from SCS may be excluded, as the selection criteria are too tight. At our centre, the current trial-to-implant rate is 91.6% with an explant rate of 6.7% (7.6% not including legacy patients). Hayek et al report a trial to implant rate of 67.8% with an explant rate of 23.9%.”

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